Going beyond memory – the dementia that affects your vision

If you ask someone to name a symptom of dementia, chances are they would mention becoming forgetful or problems with memory. While these are the most well-known symptoms of Alzheimer’s, which is the most common cause of dementia, there are some more varied and lesser known symptoms that can affect things like vision, speech, personality and behaviour. What’s more, there are other forms of dementia in which these are the primary symptoms and where memory is relatively unaffected.

One of these other forms of dementia is posterior cortical atrophy (PCA), which is a rare subtype of Alzheimer’s disease.

Why vision?

If you could look in the brain of someone with PCA, you would find some of the usual suspects implicated in Alzheimer’s – clumps of the proteins tau and amyloid. But what is different are the areas of the brain that are being affected, and as a result there are rather different symptoms. In Alzheimer’s, nerve cells in the hippocampus, the brain’s memory centre, become damaged and begin to die, causing that part of the brain to shrink. In PCA, it is the back of the brain that is affected, particularly the occipital lobe which is responsible for processing visual information.

What do we know?

In the past, researchers have suggested that there may even be several subtypes of PCA, based on the variety of visual symptoms that they have seen in people with the condition, but until now there were no studies that really explored this. At AAIC, scientists from UCL presented research investigating this interesting idea.

The team looked at scores from visual and memory tests taken by 55 people with PCA, creating three groups based on these scores. The people who scored the lowest were put into a group that they called the ‘vision’ group. The researchers split the remaining people into two groups: those who performed worse on tests of spatial processing were put in the ‘space’ group while those who had problems identifying what items were, were placed in the ‘object’ group. When the researchers then looked at MRI brain scans, they found that these three groups were associated with three distinct patterns of brain changes, suggesting that there may be different subtypes of PCA. They will need to look at this in a bigger group of people to understand whether this finding holds true and how this information could help improve future diagnosis and treatment of the condition.

A window into the brain

Trina and Graham have shared their experience of Trina’s PCA, and how it affects their everyday lives. In this video, Trina touches on how certain types of lighting can make her life a bit more problematic.

We heard at AAIC from Dr Sebastian Crutch and his team about their research using sophisticated eye-tracking equipment to examine differences in how people with PCA assess what is in front of them in a room as they make their way towards a particular place. They found that compared to people with typical Alzheimer’s, people with PCA tended to spend more time looking at parts of the room that weren’t their destination – an open door in this experiment.

In a similar experiment, the team tracked people’s movement as they made their way towards the open door to see how this was affected by the placement of lights in the room. This revealed that people with PCA were better at moving towards the open door when the light was over it. However, when the light was placed elsewhere in the room, people with PCA took a more indirect and meandering pathway towards the open door. Lessons learnt from research like this help to give guidance on how best to adapt the homes and environment of those living with PCA, supporting people to stay independent for as long as possible.

Your support is making a difference

Over the years, you’ve helped us invest over £3.7m into PCA research. Thanks to your donations, Dr Crutch and his team now have eye-tracking equipment and their ongoing work is gaining insight into visual symptoms in PCA. You are also helping Dr Chris Butler at the University of Oxford to explore the distinct way in which memory is affected in PCA, which will help to improve the way PCA can be diagnosed.

If you want to find out more about PCA, we have created a new booklet which you can download here. There is also a PCA Support Group that sends out newsletters and holds several meetings a year in different parts of the country, providing opportunities for people affected by PCA to meet and share their experiences. You can find out more and how to get involved on their website.

Hi Mel,
Thank you for your feedback.
As noted in the reply above further information about the symptoms of posterior cortical atrophy (PCA) can be found in our new booklet, linked from the original blog post.
Colour perception can be affected and our booklet advises that people with PCA may see objects in unusual colours. Someone with PCA may have good eyesight, but due to changes occurring within their brain, they may be unable to process the visual information received through their eyes correctly.
If you are concerned that your mother’s visual difficulties may be caused by PCA she may wish to contact her doctor, so further investigations can be conducted.
The following research article provides a case study account of the difficulties experienced by someone who was later diagnosed with PCA which may be of interest. However, it is important to note that each person’s experience of dementia is different:http://pn.bmj.com/content/15/1/5

One of the difficulties with PCA is that the people with it have great difficulty explaining how they see things differently. However the booklet referred to in the article explains some of the differences (see some excerpts below). Behaviours manifested by those with PCA are similar to the behaviour manifested by those with Alzheimer’s. It can vary from acceptance to denial, placid resignation to outright hostility and lashing out. Balance is very adversely affected, often accompanied by leaning to one side. As an affected person sees every change in colour or shadow, where they are walking, as a change in depth, gait is often affected by a fear of falling into holes.

In particular issues include (Excerpted from the booklet):
Recognition
Problems recognising objects or faces, especially when they’re not in plain sight.
Light sensitivity
Finding bright light uncomfortable, including glare from shiny surfaces.
Coordination
Problems with dressing and using objects like kitchen utensils and remote controls.
Thinking
Finding spelling or simple calculations hard.
Mood
Some people become low in mood, irritable or anxious, or may lose interest in things.
In PCA, the damage spreads through the brain over time, so things like memory, language and problem solving will also start to get worse.

all of the above in various degrees
dressing is the east affected apart from colour coordination but walking and movement is now becoming markedly affected.
the worst is thinking, spelling calculation(easy sort) and recognition of any thing or anyone including myself(wife)
bright light problem
mood is shocking
and cannot solve simplest of problems or plan simple tasks

one strange thing very very skin sensitive.
diagnosed feb 2017 symptoms 2-3 years prior age now male 62 yo